Effect of Cold Rolling and Heat Treatment on Properties and Microstructure of Cu-24wt%Ag Alloys

Abstract

Sheets of Cu-24wt.%Ag alloy were prepared through the process of forging, cold rolling and heat treatment to reveal the evolution of microstructures, mechanical properties and electrical conductivity. The experimental results showed that nanomultilayered structure of Cu and Ag phases arranged alternatively was obtained, with numerous nanoscale Ag precipitate-fibers embedded in Cu matrix. The lamellas in longitudinal section became curved gradually and shear bands appeared when the deformation exceeded 90.79%. With the increase of rolling strain, the average layer thickness and spacing decreased progressively and reached to less than 200 nm as the strain surpassed 96%, resulting in rapid enhancement of the hardness. The heat treatment at 250°C markedly improved electrical conductivity of the alloy, with little decline of the hardness. The anisotropy of the alloy reduced with rising temperature. Local spheroidization occurred when the alloy was heat treated at 300°C. Hardening of this Cu-Ag alloy is predominated by Cu/Ag interface in strain stage of 80%~99%, leaning mainly upon layer thickness and spacing.